Furnace for heating sheets and pairs



March 24, 1931 C. A. DAVIS ET AL FURNACE FOR HEATING SHEETS AND PAIRS 5 Sheets-Sheet l Filed March 16I /NVENTRIS @har/z5 Hg@ Bm NN\ March 24, 1931. 'c'. A. DAVIS ET AL FURNACE FOR HEATING SHEETS AND PAIRS Filed March 16,

1929 5 Sheets-Sheet 2 I .I I l I l I l I 5 Sheets-Sheet .3

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c. A. DAVIS ET AL Allllmm Filed March 16.

` FURNACE FOR HEATING SHEETS AND PAIRS March 245 1931.

March 2K4, 1931 c. A. DAvls ET AL 1,797,902

FURNACE FOR HEATING SHEETS AND PAIRs `Filed March 16, 1929 5 sheets-sheet. 4

March 24, l93 l C, A, D Avls E1- AL f 1,797,902

' FUENACE EDR HEATING SHEETS AND PAiRs 4 Filed March 16, '19,29 5 sheets-sheet 5 w/TNESS 5y afn-*- .HTTORNEYJ Patented Mar. 24, 1931 UNITE' STATES PATENT OFFICE CHARLES A. DAVIS AND FRANK E. IIZFJEIAIEY, OF YOUNGSTOWN, OHIO FURNACE FOR HEATING- SHEETS AND PAIRS Application led March 16, 1929. Serial No. 347,514.

Our invention relates to that class of furnaces employed for heating materials known in steel mill practice as sheets and pairs,- usually preparatory to subjection thereof to subsequent treatment in a rolling mill or the like7 a principal object of the invention being to provide a furnace in which greater capacity, economy of operation, and more uniform heating ofthe material may be secured 10 than in the furnaces'he'retofore usually employed for similar purposes.v

Further objects of the invention are to provide a furnace in which the gases are recirculated in such manner as to effect a desirable control of the furnace temperature and a uniform heating of the material at the minimum possible furnace temperature and in which means` are provided Afor automatically preventing air infiltration upon the opening of the furnace do-ors as far as possible as well as means for so directing any infiltrated air as to avoid oxidation and cooling of the material thereby.

Still further objects of the invention are to provide a furnace having in its preferred form but a single stack and embodying'means whereby the passage ofthe gases through the furnace to the stack can be controlled in such manner as to secure an even temperature' throughout the several chambers of the furnace; to provide a furnace in which the sheet heatingcham'ber or chambers are substantially uniformly heated throughouttheir eX- tent whereby the heated packs or sheets when edged against the side walls of the chambers or adjacent the rear of the hearth are uniformly heated throughout as -well as when disposed at the center of the hearth with consequent-elimination of what are known as rash back ends; to provide a furnace in which circulation of the gases is so effected so as to heat the furnace` hearths and thus provide what is known in theindustry as a" soft hearth without an increase in fuel eX- `pense and in which, especially in the pair heating chamber of the furnace, the gasesv 59 which in spite of precautions taken to prevent .base B of concrete or' the like .comprises at vof the heat thereof which would otherwise be lost with a resultant economy in operation, as well as the provision of a furnace of such character vand of such constructionthat its operation may be readily conducted and controlled so as to secure maximum uniformity in the heating of the material.

Our invention still further includes other objects and novel features of design, construc- -tion and arrangement hereinafter more particularly pointed out or which will be apparent to those skilled in the art fromthe fol-` lowing description of a furnace constructed inaccordance with our invention and illustra ted in the accompanying drawings.

While we have herein chosen to refer more particularly to a furnace of the tandem type, it will be understood we do, not thereby desire or intend `to coniine ourselves thereto as our invention may be embodied in furnaces of other types if desired without departing tllerefrom or sacrificing the advantages thereo In the drawings, Fig. 1 is a vertical longitudinal staggered section through the furnace on line 1 1 in 3; Fig. 2 is a topplan view of the furnace partially in horizontal section on line 2 2 in Fig. 1 and Fig. '85 3 is a horizontal section on line 3 3 in said figure.v Fig. 4 is a fragmentaryside elevation of the rear en d of the furnace showing the stack, drawing doors and adjacent parts; Fig. 5 is a fragmentary transverse section through the furnace on line 5 5 of Fig. l, and Figs. 6 and 7 are respectively similar sections on lines 6 6 and 7 7 of said figure. The same characters of referenceA are used to designate similar parts in the several figures and the directions in which the several sections are taken are indicated by the arrows 0n the section lines.

4The furnace which may be disposed on a its rear end the pair heating chamber-C and at its front end a pair of sheet heating chamber C', C disposed side by side symmetrically with respect to the pair heating chamber which is narrower than the combined width of the sheet heating chambers. The pair heating chamber comprises a bottom 1, side walls 2 and 3, end wall 4 and a roof 5 desirably transversely arched and inclined forwardly and downwardly from the end wall, all of said walls and roof7 as well as the other walls of the furnace hereinafter mentioned, being constructed of brick or other suitable material. At its forward end the pair heating chamber is closed by a transversely extending partition wall 6 which separates it from the chambers C', C" which are bounded by a vbottom 7, side walls 8 and 9. front wall 10, and a transversely arched roof 11, while the two chambers are separated longitudinally by a partition wall 12. l/Vhile we have shown a furnace embodying two sheet heating'chambers, it will of course be appreciated that in certain cases but a single sheet heating chamber may be provided .in

which case the partition Wall 12 or its equiv# aient will be omitted. The several walls of the furnace are supported by suitably disposed buckstays 13 or the like disposed at intervals thereabout and connected at their upper extremities as and where required by tie beams 14 in-the manner common to furnace construction and which therefore requires nov further description.

The pair heating chamber hearth 15 extends rearwardly from the partition wall 6 to a point adjacent the end wall 4 and extended longitudinally through this hearth is a flue 16 centrally divided by a partition 17 while above the hearth on each side of the flue, walls 18 and 19 are respectively disposed, the upper surfaces of these walls being preferably inclined upwardlyffrom the end wall toward the partition wall 6. Upon these walls 1S and 1'9 may be disposed longitudinally extending skids 20 for the reception of the pairs P which are charged into the furnace through a port 21 in theV end wall 4, beyond which the skids are desirably continued so as to facilitate the charging, and which is closed by a vertically slidable door 2 2 operated by any convenient actuating mechanism generally designated as 23. rlhrough the walls 18 and 19 below the skids ports 25 are provided at lngitudinally spaced intervals to permit free circulation of the gases from those portions of the chamber lying outside of the said walls to the central flue 16 and thus.

around and about the pairs P supported on the skids to thereby form an enveloping blanket of gas thereabout to protect them from t-he oxidizing influence of any air which may enter the furnace during the charging or drawing operations.

For introducing the heating gases into the chamber C burners 30 are disposed in -the end wall 4 preferably adjacentits top and other burners 31 are directed into the chamber through the side walls thereof adjacent said end wall so that the said gases are discharged into the chamber at that end thereof at which the 'material is charged, this arrangement permitting recirculation of the gases and facilitating uniform heating of the material at the minimum possible furnace temperature. rlfhe gases projected from these burners move through the chamber toward the partition wall 6 in the direction generally indicated by the arrows in Fig. 1 and thence pass down into the iiue 16 at the center of the hearth and circulate in and about the material being heated through the ports 25 and through the flue which is open at the top and finally pass to the stack in a manner hereinafter more fully described.

For drawing the pairs when heated to the proper degree, one'or more drawing ports 33 and 34 are provided in one of the furnace side walls adjacent the inner end of the hearth and are respectively arranged Ato be closed by vertically slidable doors 35 and 36 hereinafter more particularly In( ntioned.

For creatinar the requisite draft through the furnace and conveying the products of combustion therefrom a stack 40 is suitably mounted above the rear end of the roof 5 and supported in any convenient way as upon transversely extending beams 41 and communication from the various chambers with this stack is'effected through two iiues 42 and 43 which extend transversely across the furnace roof beneath the stack and connect with the latter, the flue 42 being operative to discharge the waste gases from the pair heatingchamber into the stack and the flue 43 to similarly discharge thereinto the gases from 'the sheet heating chambers. At its opposite ends the flue 42 branches downward- -ly through the side walls of the furnace to form branch flues 42', 42 which at their lower ends are respectively connected by longitudinal ports 44 and 45 with a header flue 46 extending transversely across the furnace adjacent the bottom of the end wall 4 and with the center of which the hearth line 16 communicates. -The lues 42 and 43 as well as their respective branches are entirely separated by-a wall 47 which extends transversely and oppositely from the hearth and is carried up on both sides of the furnace 1 between the branch lues and then transversely across the top of the furnace beneath the stack. Thus the waste `rases from the chamber C pass out of the hearth Hue ,16, separate in opposite directions in the header flue 46 and from thence pass into the branch flues 42', 42 through the ports 44 and 45 and from these branch lues into the main` ue 42 and to the stack substantially as indicated by the' arrows in Figs. 1 and 3.

The branch ues43, 43 respectively communicate at their lower ends with longitudinally extending iiues 48 and 49. formed adjacent the sides of. the hearth and respectively communicating at their forward ends with transversely extendingheader iues 50 and 51 substantially below the wall 6 which are operative to collect the waste gases from the sheet .heating chambers C, C" and direct them into the flues 48 and 49 from whence they are carried through the branch lues 43, 43 to the flue 43 and thence into the stack. Thegases for heating the chambers C', C are directed thereinto byI burners 54 desirablyA disposed in the wall 6 above the roof 5 and preferably downwardly inclined, a suiicient number ofburners being employed, of course, to secure the desired temperature within the chambers; as the arrangement and construction of bothchambers are similar, a description of one of them together with its flue arrangement will suffice for the other. Thus each chamber is provided with a rearwardly, downwardly inclined hearth 55 extending from a charging door or port 56 in the front wall 10 adapted to be closed by a vertically slidable door-57. The hearth which is desirably provided with laterally spaced skids 58 for the reception of the packs of sheets, 'extends entirely across the cha1nber and terminates at its inner end adj acent the wall 6 while beneath the hearth jare formed a pluralityof laterally spaced flues 59 which communicate at theirv inner ends respectively with the header iues 50 and 51.

Near the inner ends of each hearth a plurality of ports 60 spaced laterally and longitudinally are cut therethrough into the subjacent flues and in a similar way other ports 6l are cut through each hearth adjacent the charging door, while below the outer end of the hearth a transversely extending header flue 62 is provided and carried entirely across both chambers so as to connect with the forward ends of the lues 59. A port'63 is carried upwardly in the side wall of the furnace from each end'of this header iiue 62 to communicate with the adjacent chamber above the hearth and a vertically extending port 64 is also desirably formed in the partition wall 12 which separates the chambers and arranged to communicate with both chambers and with the subjacent header flue 62.

Thus the heated gases directedinto each chamber from the burners initially move toward Athe front wall 10 and then pass vdownwardly in large proportion through theports 6l, 63, and' 64 into the subjacent flues 59 either directly or through the header 62 so the ports 60, these heavier portions wouldl prevent this result by permitting the heavier' gases to escape directly into the subjacent iiues 59 so that irrespective of the particular position of a given pack within the heating chamber it is heated substantially uniformly and in conformity with all of the other packs therein .as an even, substantially uniform temperature is maintained throughout the chamber.

The waste gases passing from the heating chambers are carried into the header lues 50 and 5l and from thence through the iues. 48 and 49 to the branches 43', 43 of lthe stack flue 43 as above ydescribed and in their traverse of the-flues 48 and 49 give up a large part of their heat to the heart-h of the pair heating chamber thereby creating what is known as a soft or heated hearth without has hitherto in furnaces of this general character been only obtainable by the expenditure of a considerable amount of fuel over that actually required for the heating of the,

material in the furnace; in accordance with our invention, however, we are able to obtain a soft hearth by the utilization of heat which would otherwise be wasted with resultant economy of operation.

In order to properly control the circulation of the gases in the furnace so that a substantially 'even temperature can be main# tained throughout the different chambers thereof irrespective of variations in stack draft kor other variant local conditions, we provide means for individually regulating the draft through the branches of. the ues 42 and'43, said means conveniently comprising a manually operable damperv in each of the branch flues 42 and 42 and a similar damper 71 in each of the branch flues 48l and43. These dampers may be of any suitable form, that shown consistingjof a plate of refractory material so arranged that it can be slid in or out transversely of the Hue to cut down, oropen up the draft therethrough. Thus byY a suitable regulation of the dampers 70, the draft from each side of the chamber C to the stack can be controlled and in like manner the draft from each of the chambens-,`C can be similarly controlled through the dampers"7l in accordance with the particular operating conditions encountered.

ln filtration of air into furnaces in which sheets, pairs or like material are being heated is extremely undesirable as it tends to cause oXidiZation of the material, this infiltration usually taking place when the furnace doors are open for charging or drawing; it has thus been Customary to reduce air `the furnace and for a similar purpose ilues 75 may be arranged adjacent the drawing ports 33 and 34 to connect with the flue 49 so as to conduct thereto any air which may enter the furnace through the ports when their doors are open.

vWith' the same end in view, that is, the prevention of air infiltration upon the opening of thefurnace doors, we also preferably provide dampers respectively interconnected with the various furnacedoors andso disposed and arranged as to automatically cut o' the stack draft from the different furnace chamber-s in conformity with the opening of the doors thereof so that when the door of any given chamber is open a slight positive instead of a negative pressure is maintained therein so that the gases tend to rush out from the open door and thus oppose the entrance of air. f

Thus `for so controlling the draft from the chambers C', C respectively7 we provide a pair of vertically slidable dampers 76 and 77 in the flue 43 on opposite sides of the stack and respectively connect these dampers in any convenient way, as by chains 78 carried over sheaves 79 and 80, with the operating mechanism, generally designated as 8l, of the doors 57 in such manner that when either door is opened the damper controlling the draft from the chamber with which that door communicates is automatically cutoff through the flue 43A until the door is again closed. Consequently as soon as the draft is cut off from the particular chamber whose door has been opened a slight positive pressure builds up therein and some of the gas escapes out,

wardly through the door with consequent prevention of any material amount of air infiltration.

For a like purpose we also provide similar dampers 83 and 84 in the flue 42 and interconnect these dampers with the doors 35 and 36 so that when either door is open the stack draft from both sides of the'chamber C will sheaves 87 on opposite sides of the stack to a single chain 8.8 which is carried over suitably positioned sheaves 89 and downwardly to a T-s'haped weight 90 Whose arms extend in opposite directions into the pat-hs of the doors and which is arranged tol slide vertically between them. Thus wheneither door is raised by its appropriate elevating mechanism (not shown) the T-shaped weight is carried up with it and both of the flue dampers are lowered so as to close off the draft until the door is again lowered when the weight follows it down and raises the dampers, whereby, as hitherto explained, a positive pressure is maintained in the chamber C 'While either door is open with resultant escape of gas from the chamber instead of air infiltration. `While under ordinary conditions it is unnecessary to interconnect the charging door 22 with the stack draft dampers 83 and 84 so as to operate the latter upon the opening'of the former, such interconnection may be effected in any convenient way if desired; usually, however, the infiltration of a certain amount of air -at the charging end'of the chamber Where the pairs are introd-uced cold or relatively so is not particularly objectionable, especially as the major portion of it immediately pas/ses into the header 46 just inside the door and from thence to the stack.

lNe have thus provided a furnace in which by suitable recirculation of the gases we are able to heat the hearths of both the pair and sheet heating chambers without the expenditure of fuel additional to that actually required for the heating of the pairs and sheets to the desired temperature and by the use of which, through the uniformity in the heating of the pairs, the subsequent rolling operations thereon are facilitated, a better quality of sheets is produced and roll breakage lessened, while through the uniform heating of the sheets, irrespective of their particular position in the sheet heating chambers, the sheet packs are readily opened after withdrawal from the furnace and rash back ends and other imperfections substantially eliminated. By suitable manipulation of the dampers 70, the operator is at all times able to control the `draft through the pair heating chamber .in such manner as to maintain an even, substantially uniform temperature throughout the same, whilein like manner the draft from the sheet heating chambers can be individually controlled and regulated by manipulation of the dampers 7l with a like end in view whereby, although but a single stack is provided for carrying off the substantially enveloped `or surroundedby` blankets of gas, but little or no oxidation of the material takes place and, on the other hand, economy'of operation is enhanced by the avoidance of the customary practice of supplying an excessive amount of Gases to the furnace to .prevent'oxidization ofD the material, while through/the use of but asingle Stack for the combined pair and sheet heating furnace the initial cost of installation is usually reduced over thatof separate pair and sheet heating -furnaces of like capacity each provided with its own stack.

While we have vherein shown and described with considerable parti'cularity a furnace constructed in accordance with a preferred embodiment of our invention, we do not Y thereby desire or intend to confine ourselves thereto-as the principles of our invention may be utilized in furnaces of other forms and embodying an desired constructional details without sacrificing the advantages of our invention or departingifrom the spirit and scope thereof as defined by the appended claims.

` Having thus ydescribed our invention we claim and desire to protect by Letters Patent of the United States:

l'. A furnace of the class described, co1n prising separate pair and sheet heating chambers each provided with a hearth, means for introducing heating gases to each chamber, a stack, means for circulating the gases in the sheet chamber beneath the hearth thereof, thence beneathv the hearth of the pair heat- -ing chamber, and thenpe tothe stack and means for circulating the` heating gases in the pair chamber through the hearth thereof and thence to the stac 2. A furnace of the class described, comprising separate pair and sheet heating charnbers each having a hearth, a stack adapted to carry waste gases from thevfurnace, means for introducingheating gases separately to each chamber, flues for con lucting said gases beneath the hearth of the sheet heating chamber, then beneath the hearth of the pair chamber and thence to the stack, and means for effecting circulation of the gases in the pair chamber through the hearth thereof and thence to said stack.

3. A furnace of the class described, comprising separate pair-and sheet heating chambers each provided with a hearth, a stack adapted to carry the waste ases from the furnace, means for separate y introducing .heating gases to each chamber, a plurality of flues beneath the hearth of the sheet heating chamber adapted to conduct said gases beneath the hearth and toward the pair heating chamber, a fiue communicating with Said first mentioned iiues and extending adjacent the hearth of the pair heating chamber' and a fiue extending from said last mentioned flue to said stack. r

4. A furnace of the class described,lcom prising separate pair and sheet heating chambers, each having a hearth and a port for charging or drawing the material to be heated therein, movable doors for openingand closing said ports', a stack adapted to carry waste gases from the furnace, means for separately introducing heating gases to each chamber, a plurality of iiues beneath the hearth of the sheet heating chamber adapted to conduct p said gases beneath the hearth thereof and toward the pair heating chamber, a flue communicating with said first mentioned fluesl conducting the heating gases introduced to the pair heating chamber through the hearth thereof, flues on opposite sides ofthe chamber operative to then conduct said gases to thestack, and means interconnected respectively-with said doors operative to prevent the flow of gases from each chamber tothe stack when the door of such chamber is open and comprising dampers disposed in the iues leading from the several chambers tothe stack. i

` 5. A furnace of the class described,icom

prising a pair heating chamber and a plural- 'ity of sheet heating chambers each provided with a\ hearth, a stack adapted to conduct waste gases' from rthe furnace, means for introducing heating gases separately to each chamber, a plurality of iiues beneathV the' hearth of each sheet heating chamber, ports extending through said hearth into said tlues,

a flue communicating with each group of flues beneath the hearth of each sheet heating chamber extending` adjacent the hearth of the pair heating chamber and vadapted to conduct the gases from said iues and a flue communicating with each of said last mentioned iues extending to said stack.

6. A furnace of the class described, comprising a pair heating chamber and a plurality of sheet heating chambers each provided with a hearth and a port for the passage of the material to be heated therein, movable doors for opening and closing each of said ports, a. stack adapted to conduct waste gases from the furnace, means for introducing heating gases separately to each chamber, a plurality of iiues beneath the hearth of each sheet heating chamber, ports extending `through said hearths into said flues, a iue ber extending'adj acent the hearth of the pair heating chamber and adapted to conduct the gases from said flues, a flue communicating with each of said last mentioned llues and extending to said s ack, a damper in eachof said last mentione flues operable to'control the draft -from the sheet heating chamber with which such flue is in communication, and means connecting each damper with the door of 'that chamber whose iue is thereby controlled adapted to close said damper when said door is Aopen to thereby cut olf the draft from such chamber to the stack.

7. A furnace offtheclass described, com"- prisi'ng a pair heating chamber and a plurality o-f sheet heating chambers each provided with a hearth, a stack adapted to conduct waste gases from the furnace, means for introducing heating gases separate-ly to each chamber, a. plurality of iiues beneath the hearth of each .sheet heating chamber,

ports extending through saidchearth into said fines adjacent the front and'adjacent the rear ends of the latter, a flue communicating with each group of flues beneath the hearth of each sheet heating. chamber extending adjacent the hearth of the pair heating chamber and adapted to conduct the gases from said flues so as to heat said last mentioned hearth and a flue on each side'of the pair heating chamber respectively communicating witheach of said last mentioned flues and extend.- ing to said stack.

8. A furnace of the 'class described, comprising a plurality of'diiferent chambers respectively adapted for heating sheets and pairs and each having a port for charging or drawing the material to be-heated therein,

movable doors for opening and-closing said.

ports, a stack for conveying the products Vof combustion from thel furnace, lues leading from said chambers tov said stack, dampers disposed in said flues and means respectively interconnecting said dampers with said doors whereby when said doors are opened 4said dampers are operated to cut off the draft from the respective chambers to the stack.

9. A furnace of theclass described, cornprising a pair heating chamber and a sheet heating chamber each provided with a port for the passage of the material to be heated therein, a movable door adjacent each port, a stack for conveying the products of com- -bustion from the furnace, afine extending from each of said chambers to said stack, a draft-controlling damper in each of said flues, and means connecting each damper with the door of that chamber whose flue is thereby controlled adapted to: close said damper when said door is open to thereby cut oftI the draft from suchcharnber to the stack 10. In a furnace of the class described comprising a-pair heating chamber, means for introducing heating gases to -said chamber,

a hearth in said chamber, a flue extending longitudinally in the hearth, a stack, iiues communicating with said first mentioned flue and extending to the stack on opposite sides of the chamber, and a plurality of ports formed in the hearth to permit circulation of said gases between the chamber and said first mentioned flue.

l1. A furnace as specified in claim l() and having a partition extending longitudinally in the flue in the hearth and provided with a damper in each flue extending to the stack whereby the draft through said hearth flue from each side of the chamber maybe separately controlled.

12. A furnace of the class described, comprising separate pair and sheet heating chambers each having a port for the passage of the material to be heated therein, means for introducing heating gases to each of said chambers, a stack, a hearth in each chamber, means for conducting the spent gases from the sheet heating chamberadjacent the hearth in the pair heating chamber toassist in heating said hearth and thence to the stack, means for conducting the heating gases in the pair heating chamber adjacent its hearth and thence to the stack, and means automatically operative to cut of the passage of the gases from each chamber to the stack upon the opening of thelport to saidchamber and to Ypermit said hcirculation upon the closing of door for each lof said ports, means for introy ducing heating gases to each chamber, a stack,

a hearth in each `chamber, iues for permitting circulation of the heating gases introduced to the sheet heating chamber through the hearth thereof, thence adjacent the hearth of the pair heating chamber and thence to the stack, flues for permitting 4circulation of the heating gases introduced to the pair chamber through and about the hearth thereof and thence to the stackand means interconnected respectively with said doors operative to prevent the flow of gases from each chamber'to the stack when the door of such chamber is open. 14.' A furnace of the class described, comprising separate pair and sheet heatin cham bers each provided with a port for-t e passage of the material to be heated therein, a door for each of said ports, means for introducing heating gases to each chamber, a stack, a hearth in each chamber, flues for permitting circulation of the heating gases introduced to the sheet heating chamber through the hearth thereof, thence adjacent the hearth of the pair heating chamber and thence to the stack, ues for permitting circulation of the heating. gases introduced to the pair chamber through and about the hearth thereof and menace heating chamber, and means interconnected respectively with said doors operative to prevent the flow of gases from each chamber to the stack when the door of such chamber is open and comprising dampers disposed in the flues'leading from the several chambers to the stack, the dampers in the flues leading thereto from the pair chamber being simultaneously operable.

l5. A furnace of the class described, comprising separate sheet and pair heating cham bers, means for introducing heating gases to each of said chambers, a stack, a hearth in each chamber, means for circulating the heating gases introduced to the sheet heating chamber through the hearth thereof, means for thereafter conducting said gases adjacent the hearth of the pair heating chamber to assist in heating said hearth and thence to the stack, means for effecting circulation Vof the heating gases introduced to the pair heating chamber in and about the hearth thereof and then conducting said gases to the stack, said means including a longitudinally divided port in said hearth, separate iiues 0nA 

